1. Field of the Invention
The present invention relates to an image processing apparatus for reading an image on a sheet-like recording medium by applying a laser beam to the sheet-like recording medium and scanning the sheet-like recording medium with the laser beam in a main scanning direction.
2. Description of the Related Art
There is known a system for recording radiation image information of a subject such as a human body with a stimulable phosphor, and reproducing the recorded radiation image information on a photosensitive medium such as a photographic film, or displaying the recorded radiation image information on a display unit such as a CRT or the like.
The stimulable phosphor is a phosphor which, when exposed to an applied radiation (X-rays, α-rays, β-rays, γ-rays, electron beams, ultraviolet radiation, or the like), stores a part of the energy of the radiation, and, when subsequently exposed to applied stimulating rays such as visible light, emits light in proportion to the stored energy of the radiation. Usually, a sheet provided with a layer of the stimulable phosphor is used as a stimulable phosphor sheet for easy handling.
The above known system employs an image reading apparatus having a loading unit (loading device) for loading a cassette (container) which houses a stimulable phosphor sheet with radiation image information thereon, an image reading unit for reading the radiation image information carried by the stimulable phosphor sheet which has been removed from the cassette, and an erasing unit for erasing residual radiation image information on the stimulable phosphor sheet.
The above system also includes an image information reproducing apparatus for recording the radiation image information carried by the stimulable phosphor sheet and recording the read radiation image information on a photographic film (sheet-like recording medium). The image information reproducing apparatus has a loading unit (loading device) for loading a container such as a cassette or magazine which houses a photographic film, and a recording unit for recording the radiation image information on the photographic film.
The image reading unit has only one CPU for controlling the image reading unit itself, reading radiation image information, and performing various error processes as it does not have a CPU dedicated to the reading of radiation image information.
As a consequence, it is necessary to shorten a time required to detect and analyze an error with the single CPU. With the shortened time for error detection and analysis, the image reading unit is unable to perform complex error processes, and any messages produced when errors occur and actions made after errors are processed tend to be monotonous.
Actually, while each error that has occurred needs to be accompanied by an optimum error message and followed by an optimum subsequent action, the single CPU does not provide a sufficient time for such an optimum error message or subsequent action.
Another problem with the single CPU is that since it needs a dedicated counter for generating a synchronizing signal and a dedicated memory for shading correction, etc., the image reading unit is costly to manufacture.